3 Generally, the polysaccharide polymer ability to capture, bind and thus preorganizing metal ions, provides preferred nucleation and crystal growth constrained to nanoscale, allowing morphology control and preventing spontaneous particles agglomeration if the crystalline oxide is formed in solution, or sintering, if heating treatment are required for oxide crystallization. The polysaccharides interference in oxide synthesis occur in various stage of synthesis and depend both on intrinsic features like raw materials nature and extrinsic ones materialized in tunable reaction conditions. Since the project aims to analyze how polysaccharides properties may control the design/synthesis of oxide materials under various extrinsic factors, the synthetic methodology was chosen as methodological criterion. For each synthetic procedure, an in-depth characterization of the precursor, its conversion to oxide (if the reaction proceed via a precursor) and of the obtained oxide will be performed, taking advantage of the complementary scientific competences of the research team. Thus, the precursor will be characterized by elemental analysis and FTIR spectroscopy, the precursor→oxide conversion by thermal analysis, while the obtained oxide by optical (FTIR, UV-Vis, PL, Raman spectroscopy), structural (XRD), morphological (SEM, TEM, HRTEM) and specific surface investigations. The different developed synthetic approaches are focused on the synthesis of ZnO materials of nanomeric sizes and various morphologies and functionalizations using polysaccharides build up from D-glucose units linked either by α-glycosidic bonds (starch and dextran) and β-bonds (methyl-cellulose) as raw materials. The choice of these systems is not accidental. Thus, the chosen methodologies can be developed toward eco-friendly approaches, through improving their atom and energy economical (high-yield with small amounts of by-products, low energy consumption, room or low-temperatures synthesis) and minimizing hazard effect on human health and environmental (nontoxic, low cost and bio-renewable raw materials), permitting also a reliable control of the oxide products (crystallinity, purity, size, shape, morphology, functionalization) without compromising their quality, on the contrary improving it. The selected polysaccharide will allow for the first time to accomplish a comparative study concerning the dependence of oxide characteristics on polysaccharides properties. Thus, the effect of the glycosidic bond position (α and β), the polymerization degree, hydrocarbonate chain branching and distinct rheological properties will be equally analyzed. On the other hand, ZnO plays an outstanding role in many aspects of science and engineering due to its unique optical, semiconducting, catalytic and piezoelectric properties. The oxides remarkable properties, tunable through size, morphology, and functionalization, are the starting point for attractive potential applications.Abstract

4 The project implementation planYearObjectivesActivitiesResults2011Design/synthesis of ZnO nanostructures: solvent, surfactants and additives influenceThe synthesis of different ZnO structures: preliminary results-Raport2012Design/synthesis of ZnO nanostructures by precipitative and combustion procedures-The influence of synthesis experimental parameters on ZnO morphological and structural properties-Photoluminescence and photocatalytical properties-Book chapter-article-participation to national and international conferences2013Design/synthesis of ZnO nanostructures by hydrothermal procedures using polysaccharides as hard-template- The influence of synthesis experimental parameters on template’s size and shape-The influence of deposition techniques on ZnO structural and morphological properties-The use of template for the synthesis of solid and hollow ZnO structures-Book-articles2014-ZnO obtained by hydrothermal procedure using polysaccharides as soft-template-ZnO obtained by gel-template procedures using polysaccharides2015-ZnO obtained by forced hydrolysis proceduresFor all two synthesis protocols will be investigated :

6 Project obiectivesThe general scientific objective is focused on the developing of innovative environmental friendly strategies polysaccharides-assisted, for the design and synthesis of tailor made oxide-based nanomaterials, exploiting either individually or simultaneously polysaccharides diverse and versatile properties. The project’s specific objectives that constitute also novelty features belonging both to fundamental and applicative research, are as follows:to establish a relationship with a large degree of generalization between polysaccharide peculiarities - synthesis methodology - oxide features, in order to detect a general trend, forwarding polysaccharide-assisted design and synthesis topic;to develop environmentally friendly protocols for the synthesis of nanosized ( Å) ZnO materials, functionalized or not with polysaccharides;to develop environmentally friendly protocols for the synthesis of ZnO spherical structures such as sphere, core/shell, hollow sphere and jingle-bell;to develop environmentally friendly protocols for the synthesis of ZnO/C composites.Besides these scientific objectives (original results in areas of interest and perspective), objectives like international visibility increasing (by publication in journal of high impact factor and participation to prestigious international conference), young researchers motivation (by financial advantages) as well as infrastructure improvement and supplies purchase have to be mentioned.

9 The synthetic protocols and used carbohydrates:the building of a green methodsAlthough some progress regarding the involvement of saccharides in materials synthesis has been already made, the identification, investigation and development of carbohydrates assisted synthetic routes is (unfortunately) an insufficiently explored research topic of the chemistry. Following a small steps approach, we selected for the start polisaccharides having in common the presence of D-glucose units: polysaccharides starch and dextran containing D-glucose units linked by α-glycosidic bonds and, methylcellulose constituted from D-glucose units linked by β-bonds.

10 2. The main precipitation synthetic methodologies developed with posyccharides as soft templatezincsourceprecipitationagent 1agent 2starchdextranmetyl-cellulose

11 2.1 Zn2+-starch system: model systemVarious hierarchical spherical shaped assemblies ZnO structures were successfully synthesized via a simple, low-cost starch-mediated precipitation method. It was proved that starch is the key parameter for the synthesis of pure ZnO material with spherical morphologies. The temperature increase lead to a variation of ZnO stoichiometry and implicit its associated defects that determine an interesting change of the optical properties (band gap, photoluminescence characteristics). While ZnO-starch composites obtained initially after the synthesis reaction performed at 80oC are of 5-7 spheres aggregates with diameters of 100 to 500 nm, after the calcination (500oC) their morphologies change into a donut-like ones which centered-located holes shrinks to extinction with further temperature rising (800oC). The donut morphology is connected with the highest surface area and total pore volume. The oxide obtained after calcinations at 500oC demonstrated excellent photodegradation ability under visible light irradiation, a total mineralization of phenol being achieved. Such properties is caused by a combination of relatively significant specific surface area due to its donut morphology, high crystallinity and a favorable combination of defects for band narrowing that permit a enhanced light utilization rate.

15 2.2 Zn2+-methylcellulose and Zn2+-dextran systemsThe developed green synthetic protocols lead to diverse morphologies: spherical, spindle, rod ones.The influence of the synthesis parameters (time, temperature, raw materials nature and ratio, precipitation agent, initial pH and its evolution during the synthesis, ultrasound irradiation) on the shape, size and porosity of the obtained ZnO-based composites is investigated.The thermoreactivity of the synthesized composites is scrutinized.The possibility of obtaining ZnO/C composites is also analyzed, establishing the parameters of polysaccharide  carbon containing materials conversion, degree of crystallization/graffitization, influence of Zn2+ amount on final material quality.The optical properties of the ZnO based materials were analyzed by UV-Vis and photoluminescence spectroscopy.A formation mechanism for each system was advanced, evidencing the auto-assembling processes.The composites, either ZnO-saccharide and ZnO/C were tested as photocatalysts and antimicrobian agents, establishing different correlations between the optical properties and the efficiency in these applications.For same composites, electrochemical investigations (linear sweep voltammetry, electrochemical activity analysis) were also performed.One article is in preparation : Methylcellulose based synthesis for ZnO with spindle like morphologies, R.Dumitru, J.M.Calderon-Moreno, R.Birjega, O.Carp.

16 3. Polysaccharides as combustion agents for ZnOIn this synthetic procedure the polysaccharides act as high temperature fuels. The obtained ZnO crystallites are larger than those obtained by precipitate method, the specific surface lower (2-4 m2 /g), but the activity in photocatalytic degradation reactions tested for phenol and resorcinol are particularly good, a 100% mineralization of pollutants being achieved. The obtained data are the subject of an article in preparation.SEM images of ZnO: (A) starch-Zn(NO3)2; (B) cellulose-Zn(NO3)2;(C)Sta rch-Zn(CH3COO)2; (D)cellulose-Zn(CH3COO)2

17 SEM images of carbonaceous4. Polysaccharides as hard templates for ZnO spherical structures:Hard templates syntheses are generally used for obtaining hollow structures. In principle, regardless of the used methodology, the synthesis procedure should include three stages: - hard-template synthesis;introduction /deposition on template surface of the metallic cations; - the remove of the hard-template by further processing (usually thermal ones).We utilized several introduction techniques as impregnation, ultrasound irradiation, or a double deposition (impregnation and impregnation). The diameter and the wall thickness of the obtained spherical morphology, its type (solid or hollow) and porosity depend on the synthesis and calcination parameters.Our research showed for the first time that the template generated by polysaccharides can also function as a template in obtaining solid oxide spherical structures (solid spheres) and also for metal oxide / C composites preserving the same morphology.The scheme of hydrothermal processSEM images of carbonaceoussphere templates4.1 Template synthesis

22 5. Polysaccharides as soft templates for ZnO/saccharide compositesThe developed one-pot synthetic procedure is green both regarding utilized raw materials [zinc acetate as zinc source, carbohydrates (glucose, fructose, sucrose, dextran, starch and methylcellulose)as growth inhibitors and crystal habit modifiers], and synthetic methodology (mild hydrothermal procedure carried out at low temperature for a short period of time). The general character of the method derives from the possibility of using either mono, di- or polysaccharides that contains D-glucose units. Because the nature of the saccharide rules the construction features of the ZnO structures (rods spindles, hollow and solid spheres), the ability to use various carbohydrates adds to this method a high versatility. The enhanced photocatalytical and antimicrobial performances indicate the great potential of the ZnO based composites in relevant water detoxification and biomedical applications. Correlating the ZnO_SAC antimicrobial activity with the photocatalytical one, and also with their photoluminescence peculiarities we were able to identify that the mechanism of the biocidal action toward the two investigated bacterial strains follows different paths.An article “Green synthesis for green materials: ZnO-saccharide composites for environmental remediation and antimicrobial applications”, A.Stan, C.Munteanu, R.Ene, E.M.Anghel, A.M. Musuc, R.Birjega,A. Ianculescu, I.Raut, L.Jecu, M.Badea Doni, O.Carp, is submitted to Chemistry-An European Journal

33 ArticleSynthesis, characterization and thermoreactivity of some methylcellulose-zinc compositesAdina Magdalena Musuc, Raluca Dumitru, Alina Stan, Cornel Munteanu, Ruxandra Birjega and Oana CarpJournal of Thermal Analysis and Calorimetry, (submitted, minor revisions)AbstractTwo methylcellulose-ZnO and one methylcellulose-Zn2+ composites were obtained by precipitation and hydrothermal procedures. The thermal behavior of the composites was examined by simultaneous TG, DTG, DSC-FTIR thermal method. It was found that the thermal reactivity of the methylcellulose contained by the composites is strongly dependent on the composites’ synthetic procedure, but in all cases its stability is shifted toward lower temperatures. For each type of composites, the causes that lead to a change of methylcellulose thermoreactivity were highlighted. The structural, morphological and optical characteristics of the ZnO_based materials are also demonstrated.Keywords: Methylcellulose, Zinc-methylcellulose composites, Thermoreactivity